001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.configuration.beanutils;
018
019 /**
020 * <p>
021 * The default implementation of the <code>BeanFactory</code> interface.
022 * </p>
023 * <p>
024 * This class creates beans of arbitrary types using reflection. Each time the
025 * <code>createBean()</code> method is invoked, a new bean instance is
026 * created. A default bean class is not supported.
027 * </p>
028 * <p>
029 * An instance of this factory class will be set as the default bean factory for
030 * the <code>{@link BeanHelper}</code> class. This means that if not bean
031 * factory is specified in a <code>{@link BeanDeclaration}</code>, this
032 * default instance will be used.
033 * </p>
034 *
035 * @since 1.3
036 * @author Oliver Heger
037 * @version $Id: DefaultBeanFactory.java 439648 2006-09-02 20:42:10Z oheger $
038 */
039 public class DefaultBeanFactory implements BeanFactory
040 {
041 /** Stores the default instance of this class. */
042 public static final DefaultBeanFactory INSTANCE = new DefaultBeanFactory();
043
044 /**
045 * Creates a new bean instance. This implementation delegates to the
046 * protected methods <code>createBeanInstance()</code> and
047 * <code>initBeanInstance()</code> for creating and initializing the bean.
048 * This makes it easier for derived classes that need to change specific
049 * functionality of the base class.
050 *
051 * @param beanClass the class of the bean, from which an instance is to be
052 * created
053 * @param data the bean declaration object
054 * @param parameter an additional parameter (ignored by this implementation)
055 * @return the new bean instance
056 * @throws Exception if an error occurs
057 */
058 public Object createBean(Class beanClass, BeanDeclaration data,
059 Object parameter) throws Exception
060 {
061 Object result = createBeanInstance(beanClass, data);
062 initBeanInstance(result, data);
063 return result;
064 }
065
066 /**
067 * Returns the default bean class used by this factory. This is always
068 * <b>null</b> for this implementation.
069 *
070 * @return the default bean class
071 */
072 public Class getDefaultBeanClass()
073 {
074 return null;
075 }
076
077 /**
078 * Creates the bean instance. This method is called by
079 * <code>createBean()</code>. It uses reflection to create a new instance
080 * of the specified class.
081 *
082 * @param beanClass the class of the bean to be created
083 * @param data the bean declaration
084 * @return the new bean instance
085 * @throws Exception if an error occurs
086 */
087 protected Object createBeanInstance(Class beanClass, BeanDeclaration data)
088 throws Exception
089 {
090 return beanClass.newInstance();
091 }
092
093 /**
094 * Initializes the newly created bean instance. This method is called by
095 * <code>createBean()</code>. It calls the
096 * <code>{@link BeanHelper#initBean(Object, BeanDeclaration) initBean()}</code>
097 * of <code>{@link BeanHelper}</code> for performing the initialization.
098 *
099 * @param bean the newly created bean instance
100 * @param data the bean declaration object
101 * @throws Exception if an error occurs
102 */
103 protected void initBeanInstance(Object bean, BeanDeclaration data)
104 throws Exception
105 {
106 BeanHelper.initBean(bean, data);
107 }
108 }